How close did the nation come to a second Civil War in 1868? We’ll talk this hour with historian and attorney David O. Stewart, whose new book is “Impeached: The Trial of President Andrew Johnson and the Fight for Lincoln’s Legacy” (Simon and Schuster, 2009).

221 years ago, a group of men gathered in Philadelphia to frame our nation’s government. What was the process like? We’ll look back this hour with David O. Stewart, author of “The Summer of 1787: The Men Who Invented the Constitution” (Simon and Schuster Paperbacks, 2008).